how did you used to commute? >> like everybody else: drive over the bridge. >> reporter: no big deal? >> no big deal. >> reporter: that's the lake champlain bridge between new york and vermont, when there still was a bridge. f.d.r. opened it in 1928 and it carried as many as 4,000 vehicles a day, until last fall when, with almost no warning, it was closed. the american society of civil engineers issues a report card every four years on the state of america's infrastructure. and the last one in 2009 was not good at all. the overall grade was a "d." "d?" that's as good as it gets? >> and it's not getting any better. back in 2005 we also did a report card and it was also a "d," there so we haven't gained any ground. >> reporter: andrew hermann helped write the report card which examined every aspect of the country's infrastructure. bridges got a "c," but even with that average grade, 12% of them- - more than 72,000 bridges-- are too old, or what's politely called "structurally deficient." >> it means we've been igno